Networking communication method of cellular passive frequency division multiplexing ultrahigh frequency RFID system

Abstract

The invention discloses a networking communication method for a cellular passive frequency division multiplexing ultrahigh-frequency RFID (Radio Frequency Identification) system, which is applied to the field of communication and aims at solving the problem that the communication efficiency and reliability of the system are further influenced due to the fact that collision of system communication signals and interference sources of a base station receiving end are aggravated due to contraction of a working frequency band. The invention provides a cellular passive frequency division multiplexing ultrahigh frequency RFID system multi-band synchronous networking access method and a system multi-device channel cooperative switching networking access method, designs a base station-auxiliary base station wireless networking protocol, standardizes the system network communication process, and improves the system communication efficiency. The reliability and the stability of long-distance efficient identification communication work of the cellular passive frequency division multiplexing ultrahigh frequency RFID system are ensured, and then the passive UHF RFID internet-of-things system with low cost and wide area coverage is realized.

Description

Technical Field

[0001] The invention belongs to the field of communication, and in particular relates to a RFID system networking communication technology. Background Art

[0002] Radio Frequency Identification (RFID) technology has become the cornerstone of the Internet of Things (IoT) by identifying physical objects through wireless communication. With the country proposing to "promote the comprehensive development of the IoT, incorporate the IoT into the seven key industries of the digital economy, and make arrangements for IoT access capabilities and key field applications," the theory and industry of RFID technology have gradually matured and improved. According to the different working frequencies, RFID technology can be divided into four main types: low frequency (125 / 134kHz), high frequency (13.56MHz), ultra-high frequency (860-960MHz) and microwave (2.4 / 5.8GHz). Low-frequency and high-frequency RFID technologies use the near-field coupling principle, which is suitable for close-range identification and is currently the most widely used. Ultra-high frequency (UHF) RFID and microwave RFID use the far-field coupling principle and have the ability of long-range identification and high-speed transmission.

[0003] The traditional UHF RFID system adopts a transceiver integrated architecture (also known as a two-point architecture), and the reader integrates a backscatter receiver and a carrier exciter, which results in key problems such as small reader coverage, strong self-interference between the same frequency of transceiver and transmitter, and low system communication efficiency. This leads to a separate transceiver system architecture (also known as a three-point architecture), that is, a backscatter receiver (also known as a base station) and a carrier exciter (also known as an auxiliary base station) are set up separately, and the carrier exciter is arranged around the terminal (tag) to expand the system coverage. The existing three-point UHF RFID system mainly uses time division multiplexing for data communication, that is, the base station can only receive the backscatter signal of one tag at the same time or send instructions to an auxiliary base station. Therefore, data transmission in the system is subject to the limitation of communication time slots. When multiple tags respond to the reader at the same time, tag signal conflicts will occur, and the reader will find it difficult to correctly parse the tag information or tag information recognition errors will occur, which seriously affects the system throughput. When the base station detects a conflict, according to the UHF RFID standard protocol specification, the tag needs to reselect a random time slot value, and the base station needs to execute the corresponding state jump and protocol command issuance to restart the tag identification process, which further affects the communication efficiency of the three-point UHF RFID system.

[0004] According to the latest spectrum division standard of the Ministry of Industry and Information Technology, the current UHF RFID system can only communicate in the 920-925MHz frequency band. The shrinkage of the working frequency band has aggravated the collision of system communication signals and the interference source at the base station receiving end, further affecting the communication efficiency and reliability of the system. At the same time, due to the performance limitations of existing domestic discrete devices, if the system communication frequency band and communication process are not reasonably designed, it will be difficult to meet the timing specifications of the system link work in the standard protocol. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a cellular passive frequency division multiplexing ultra-high frequency RFID system networking communication method.

[0006] The technical solution adopted by the present invention is: a cellular passive frequency division multiplexing ultra-high frequency RFID system networking communication method, the cellular passive frequency division multiplexing ultra-high frequency RFID system includes: a host computer, a base station, multiple auxiliary base stations deployed within the coverage area of ​​the base station, and electronic tags within the coverage area of ​​each auxiliary base station; the auxiliary base station acts as a carrier exciter, and the auxiliary base station excites the electronic tags within the coverage area according to the forwarding signal of the base station; the electronic tag performs reflection after the frequency offset is superimposed on its corresponding excitation carrier frequency point, and the base station acts as a backscatter receiver, and specifically adopts a multi-band synchronous networking access method, including the following processes:

[0007] First, the system is initialized. The base station uses USB2.0 to realize two-way information exchange with the host computer. The host computer writes all auxiliary base station IDs within the base station coverage area into the auxiliary base station ID list in the base station memory.

[0008] The host computer first sends the sub-channel division information of each auxiliary base station to the base station;

[0009] The base station activates a specific auxiliary base station through the auxiliary base station ID under the initialization channel configuration and transmits the available channel information;

[0010] The auxiliary base station that matches its own ID returns a confirmation beacon on the specified channel to complete the activation, while the inactivated auxiliary base station continues to listen to the next command signal from the base station.

[0011] After the auxiliary base station networking is completed, the activated auxiliary base stations excite the electronic tags within the coverage area in their respective channels and forward the base station commands;

[0012] After the electronic tags within the coverage of different auxiliary base stations receive the inventory command, they reflect their own information after superimposing the random frequency shift within the sub-channel range on the basis of the excitation carrier frequency point. The base station simultaneously receives and parses the reflected information of tags from multiple channels. The electronic tags that have not received the confirmation beacon matching their own ID wait for the next inventory command and reselect the channel to respond.

[0013] The base station transmits the counted electronic tag's own binding information and the corresponding auxiliary base station ID and other information back to the host computer.

[0014] When the number of allocated channels is less than the number of auxiliary devices currently required for networking; it also includes the processing process of shared communication channels. When the base station monitors the current networking status for a preset working time, the current signal is allocated to the auxiliary devices that have not been connected based on the recognition efficiency of each channel at the current stage.

[0015] If the recognition efficiency of a certain channel at the current stage is greater than or equal to the first proportion of the average recognition efficiency, the auxiliary device connected to the current channel is retained, or the current signal is reallocated to a random non-connected auxiliary device within a first distance range from the connected auxiliary device.

[0016] If the recognition efficiency of a certain channel at the current stage is less than the first proportion of the average recognition efficiency, the current channel is reallocated to a random non-connected auxiliary device outside the first distance range from the connected auxiliary device.

[0017] Beneficial effects of the present invention: The present invention aims at the system heterogeneous networking of multiple auxiliary base stations in a cellular passive frequency division multiplexing ultra-high frequency RFID system, and carefully designs the networking access method and corresponding communication protocol of multiple auxiliary base stations in the system, proposes a multi-band synchronous networking access method for a cellular passive frequency division multiplexing ultra-high frequency RFID system, and a networking access method for coordinated channel switching between multiple devices in the system, designs a corresponding base station-auxiliary base station wireless networking protocol, standardizes the system network communication process, ensures the reliability and stability of the long-distance and efficient identification communication work of the cellular passive frequency division multiplexing ultra-high frequency RFID system, and thus realizes a passive UHF RFID Internet of Things system with low cost and wide area coverage. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a three-point UHF RFID system;

[0019] Figure 2 This is a schematic diagram of the deployment of a cellular passive frequency division multiplexing UHF RFID system;

[0020] Figure 3 A flowchart of a method for assisting base station multi-band synchronous networking communication;

[0021] Figure 4 The present invention is a flow chart of a networking communication method for assisting coordinated channel switching between base stations. DETAILED DESCRIPTION

[0022] To facilitate those skilled in the art to understand the technical content of the present invention, the present invention is further explained below with reference to the accompanying drawings.

[0023] Under the background of the current passive UHF RFID system's shrinking operating frequency band and the performance limitations of domestic discrete devices, the system has problems such as low communication efficiency, terminal identification blind spots, small base station coverage, and strong self-interference between transmitting and receiving at the same frequency. The present invention aims at the heterogeneous networking of multiple auxiliary base stations in a cellular passive frequency division multiplexing ultra-high frequency RFID system, proposes a multi-band synchronous networking access method for a cellular passive frequency division multiplexing ultra-high frequency RFID system, and a channel coordinated switching networking access method between multiple devices in the system, designs a base station-auxiliary base station wireless networking protocol, standardizes the system network communication process, ensures the reliability and stability of the long-distance and efficient identification communication work of the cellular passive frequency division multiplexing ultra-high frequency RFID system, and thus realizes a passive UHF RFID Internet of Things system with low cost and wide area coverage.

[0024] The architecture of UHF RFID system with separate transceiver (also called three-point type) is as follows: Figure 1 As shown in the figure, it mainly includes four parts: host computer, base station, auxiliary base station, and electronic tag. The existing three-point UHF RFID system mainly uses time division multiplexing for data communication. The base station can only receive the backscatter signal of one tag or send instructions to an auxiliary base station at the same time. The system data transmission is still limited by the current communication time slot state. When multiple tags respond to the reader command at the same time, a tag signal collision will occur. The reader is difficult to correctly parse the tag information or it is easy to make tag information recognition errors, which seriously affects the system throughput. When the base station detects a conflict, according to the UHF RFID standard protocol specification, the tag needs to re-select a random time slot value, and the base station needs to execute the corresponding state jump and protocol command issuance to restart the tag identification process, which further affects the communication efficiency of the three-point UHF RFID system.

[0025] According to the new regulations of the Ministry of Industry and Information Technology, the current UHF RFID system can only operate in the 920-925MHz frequency band. This frequency band is too narrow, and the transmission data rate is limited by the performance of existing RFID radio frequency chips. If the base station-auxiliary base station communication and the auxiliary base station excitation tag communication frequency band and communication process are not reasonably designed, signal collisions are likely to occur in the full-duplex system communication, making it impossible for the tag to correctly receive the command forwarded by the auxiliary base station, the base station receiving end cannot correctly interpret the tag reflection signal, and it is difficult to meet the timing requirements of the standard protocol for system operation. Therefore, the present invention aims at the system heterogeneous networking of multiple auxiliary base stations in the cellular passive frequency division multiplexing ultra-high frequency RFID system, and carefully designs the networking access method and corresponding communication protocol of multiple auxiliary base stations in the system, proposes a multi-band synchronous networking access method for the cellular passive frequency division multiplexing ultra-high frequency RFID system, and a networking access method for coordinated channel switching between multiple devices in the system, designs a corresponding base station-auxiliary base station wireless networking protocol, standardizes the system network communication process, ensures the reliability and stability of the long-distance and efficient identification communication work of the cellular passive frequency division multiplexing ultra-high frequency RFID system, and thus realizes a passive UHF RFID Internet of Things system with low cost and wide area coverage.

[0026] The present invention proposes a cellular passive frequency division multiplexing UHF RFID system based on domestic discrete devices. Figure 2 As shown. Multiple auxiliary base stations (Helpers) are distributedly deployed within the coverage area (BS Work area) of the base station (Base-Station). The auxiliary base station acts as a carrier exciter, mainly demodulating the base station signal to complete the system networking access and realize direct forwarding or frequency conversion forwarding functions. The signal forwarded by the auxiliary base station will excite the electronic tag (Tag) within its coverage area (H Work area). The tag realizes the data parallel transmission function by backscattering the radio frequency carrier of the auxiliary base station, and the base station acts as a backscattering receiver to simultaneously receive and analyze the ID and other information reflected by the electronic tag. Considering the possible scenarios in the operation of the cellular IoT system, a variety of auxiliary base station networking access methods and corresponding communication protocols are designed to ensure the reliability and stability of the system operation.

[0027] Design a multi-band synchronous networking communication method for auxiliary base stations such as Figure 3As shown, the system is initialized first. The base station uses USB2.0 to realize two-way information interaction with the host computer. The host computer writes all auxiliary base station IDs within the coverage of the base station into the base station memory (Helper ID list). When the auxiliary base station has not changed, that is, the available auxiliary base stations within the coverage of the base station have not been added or removed, the host computer may not change the auxiliary base station ID list in the base station. The host computer first sends the sub-channel division information of each auxiliary base station to the base station to start the networking process. The base station activates a specific auxiliary base station through the auxiliary base station ID under the initialization channel configuration and transmits the available channel information. The auxiliary base station matching its own ID returns a confirmation beacon on the specified channel, thereby achieving the function of the auxiliary base station accessing the system network (i.e., auxiliary base station networking), while the unactivated auxiliary base station continues to listen to the next command signal of the base station. After judging that the auxiliary base station networking is completed, that is, all the auxiliary base station IDs of the allocated channels have returned confirmation beacons, the activated auxiliary base stations excite the tags within the coverage of their respective channels and forward the base station commands, so that the base station can simultaneously count multiple tags covered by different auxiliary base stations. After the tags within the coverage of different auxiliary base stations are parsed to the inventory command, they reflect their own information after superimposing the random frequency shift within the sub-channel range on the basis of the excitation carrier frequency. The base station simultaneously receives and parses the reflected information of tags from multiple channels. Tags that have not received a confirmation beacon that matches their own ID wait for the next inventory command and reselect a channel to respond. The base station transmits the inventory tag's own binding information and the corresponding auxiliary base station ID and other information back to the host computer.

[0028] The above system workflow is the situation where multiple auxiliary base stations within the coverage of the base station work in frequency division at the same time. However, due to the current shrinkage of available frequency bands in the UHF RFID system, when the system is deployed on a large scale or the data transmission bandwidth requirements are high, it is impossible to guarantee sufficient spectrum resources, that is, the available frequency band resources do not match the number of auxiliary base stations / transmission demand bandwidth. It also includes interference such as multipath effects when devices in certain physical locations use certain frequency bands to communicate, resulting in low recognition efficiency. At this time, the frequency band can also be switched to improve recognition efficiency, so there is such a switching decision condition. In order to ensure the continuity and stability of the system's efficient recognition work, some auxiliary base stations will share the communication channel. At this time, some auxiliary base stations within the coverage of the base station will work in a time-sharing manner, that is, the system operation process will involve switching networking access between multiple auxiliary base stations, thereby realizing the inventory recognition of more regional tags.

[0029] To solve this problem, a low-latency channel cooperative switching networking communication method between multiple devices is designed, such as Figure 4As shown, the switching of the auxiliary base station network can be specified by the host computer command, or the base station can initiate the switching autonomously. The switching process specified by the host computer command is consistent with the multi-band synchronous networking method, that is, each round of networking is started by the base station receiving the host computer networking command, and the base station sends a networking signal carrying the updated networking channel division information and the ID of the auxiliary base station in this round of networking under the default communication channel configuration. The auxiliary base station with the matching ID starts to perform the forwarding task after being confirmed to be activated. The auxiliary base station that is not activated or removed from the system in this round of networking clears the channel allocation information and continues to listen to the base station command. The base station autonomously initiates the switching networking process based on the preset switching time interval. The preset value design of the network switching interval can use the host computer to estimate the number of tags to be identified in real time, and the recognition efficiency in the continuous sliding monitoring stage as the judgment condition, and dynamically update it according to the weight setting of different conditions. The channels involved in the coordinated switching can use the recognition efficiency of each channel stage and the physical location of the auxiliary base station occupying the channel as the selection condition. If the recognition efficiency of the channel stage is high, it is planned to retain the current access device or allocate it to the auxiliary base station closer to the current access device, and vice versa. When the base station monitors the current networking status for a preset working time, it selects the corresponding ID from the stored auxiliary base station ID list according to the channel coordination selection information to construct a complete switching networking command and execute the command issuing function, and at the same time returns the switching networking information to the upper computer.

[0030] In this embodiment, the preset switching time interval is calculated as follows:

[0031] Preset switching time interval = f1*number of tags to be identified + f2*identification efficiency

[0032] Among them, f1 and f2 are weights;

[0033] If the switching interval is 1h, it means that the switching is performed every 1h, and the working time is also 1h.

[0034] Assuming that the minimum time unit is s, the average recognition efficiency of a system is 50 / s, and the recognition efficiency in the current monitoring stage is 30 / s, which is 60% of the average recognition efficiency of the system. It is estimated that the current number of tags to be identified is 5000. If the goal is to reduce the total recognition time, the design weights f1=1 / 50, f2=log0.6 can be based on the principle that the number of tags to be identified is proportional to the switching time, and the recognition efficiency is inversely proportional to the switching time. Then the preset switching time interval = (1 / 50)*5000+(log0.6)*30=85s, and the calculation result can be rounded according to the minimum time unit.

[0035] In this embodiment, recognition efficiency = the number of terminals (tags) recognized per unit time.

[0036] In this embodiment, if the recognition efficiency is greater than or equal to 80% of the average recognition efficiency, the recognition efficiency is considered to be high, otherwise the recognition efficiency is considered to be low. In practical applications, the proportion of the average recognition efficiency can be adjusted as needed to adjust the classification of high and low recognition efficiencies.

[0037] When the recognition efficiency is high, the current channel is allocated to a random auxiliary device within the first distance range from the currently connected auxiliary device; when the recognition efficiency is low, the currently connected channel is allocated to a random auxiliary device that is beyond the first distance range from the current auxiliary device. In this embodiment, the first distance range is the distance between the auxiliary devices closest to the currently connected auxiliary device. If there are multiple auxiliary devices closest to the currently connected auxiliary device, an auxiliary device is randomly selected.

[0038] If the transmission delay is ignored, T=T'. To ensure that there is no signal loss in transmission, it is necessary to ensure that the starting point T1 of each round of switching networking in the system is greater than or equal to an integer multiple of T4. The base station caches commands according to this principle, and the instruction switching and preset switching priority definition control the execution of the switching networking process.

[0039] The networking command data frame sent by the base station consists of a command code, device quantity, device parameters, frequency band information, and CRC check bits, as shown in Table 1.

[0040] Table 1 Base station networking command data frame structure

[0041]

[0042] After receiving the base station networking command, the auxiliary base station transmits a response signal to the base station on the designated channel. The response data frame consists of a response code and response parameters, as shown in Table 2.

[0043] Table 2 Auxiliary base station response data frame structure

[0044]

[0045] After each data frame is established, a delimiter and a seeker are added before it can be sent. When the ID parameter in the auxiliary base station response signal received by the base station matches, it means that the Helper being controlled by the base station is already in an activated state. The base station can send other function commands, and the activated Helper will forward the base station command.

[0046] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the scope of protection of the present invention is not limited to such specific statements and embodiments. For those skilled in the art, the present invention may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A cellular passive frequency division multiplexing ultra-high frequency RFID system networking communication method, characterized in that: The cellular passive frequency division multiplexing ultra-high frequency RFID system includes: a host computer, a base station, multiple auxiliary base stations deployed within the coverage area of ​​the base station, and electronic tags within the coverage area of ​​each auxiliary base station; the auxiliary base station acts as a carrier exciter, and the auxiliary base station excites the electronic tags within the coverage area according to the forwarding signal of the base station; the electronic tag performs reflection after superimposing the frequency offset on its corresponding excitation carrier frequency point, and the base station acts as a backscatter receiver, and specifically adopts a multi-band synchronous networking access method, including the following processes: First, the system is initialized. The base station uses USB2.0 to realize two-way information exchange with the host computer. The host computer writes all auxiliary base station IDs within the base station coverage area into the auxiliary base station ID list in the base station memory. The host computer first sends the sub-channel division information of each auxiliary base station to the base station; The base station activates a specific auxiliary base station through the auxiliary base station ID under the initialization channel configuration and transmits the available channel information; The auxiliary base station that matches its own ID returns a confirmation beacon on the specified channel to complete the activation, while the inactivated auxiliary base station continues to listen to the next command signal from the base station.

2. The cellular passive frequency division multiplexing ultra-high frequency RFID system networking communication method according to claim 1, characterized in that: After the auxiliary base station networking is completed, the activated auxiliary base stations excite the electronic tags within the coverage area in their respective channels and forward the base station commands; After the electronic tags within the coverage of different auxiliary base stations receive the inventory command, they reflect their own information after superimposing the random frequency shift within the sub-channel range on the basis of the excitation carrier frequency point. The base station simultaneously receives and parses the reflected information of tags from multiple channels. The electronic tags that have not received the confirmation beacon matching their own ID wait for the next inventory command and reselect the channel to respond. The base station transmits the counted electronic tag's own binding information and the corresponding auxiliary base station ID and other information back to the host computer.

3. The cellular passive frequency division multiplexing ultra-high frequency RFID system networking communication method according to claim 1, characterized in that: It also includes the processing of shared communication channels. When the base station monitors the current networking status for a preset working time, it allocates the current channel to the auxiliary devices that have not been connected according to the recognition efficiency of each channel at the current stage.

4. The cellular passive frequency division multiplexing ultra-high frequency RFID system networking communication method according to claim 3, characterized in that: If the recognition efficiency of a certain channel at the current stage is greater than or equal to the first proportion of the average recognition efficiency, the auxiliary device connected to the current channel is retained, or the current signal is reallocated to a random non-connected auxiliary device within a first distance range from the connected auxiliary device.

5. The cellular passive frequency division multiplexing ultra-high frequency RFID system networking communication method according to claim 4, characterized in that: If the recognition efficiency of a certain channel at the current stage is less than the first proportion of the average recognition efficiency, the current channel is reallocated to a random non-connected auxiliary device outside the first distance range from the connected auxiliary device.

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